Isolators are used in motorcycle rear wheel drives in order to reduce the noise, vibration and harshness (NVH) that may otherwise be transmitted to the rider.
Prior art couplings transmit axial loads from the sprocket to wheel shaft bearings due to the means of containing the vibration isolating materials within the sprocket hub. Axial loads can cause premature failure of the wheel bearings.
Representative of the art is U.S. Pat. No. 5,240,087 (1993) which discloses a one-sided rear swing arm suspension system for a motorcycle having a chain-driven rear wheel, in which the tension of the drive chain may be adjusted without affecting the ride height of the motorcycle. The suspension system includes a rear swing arm that is pivotably attached to the body of the motorcycle, and which extends rearwardly around and alongside the rear wheel. The rear end of the swing arm includes elongate recesses which guide and receive an adjustment yoke. The rear wheel is journalled on a spindle that extends transversely from the adjustment yoke. The yoke is positionable longitudinally on the swing arm by means of an adjustment stud extending from the swing arm, and a corresponding adjustment nut entrapped in the neck of the yoke. A single adjustment clamp nut on the end of the spindle operates to secure the spindle to the yoke and to also secure the yoke to the swing arm at a selected position corresponding to a desired chain tension.
Reference is also made to copending U.S. patent application Ser. No. 11/726,091 filed Mar. 21, 2007, published as U.S. Patent Application Publication No. 2008/0234080 A1, directed to a wheel isolator.
What is needed is a wheel isolator coupling comprising a sprocket which imparts no axial force to a sprocket bearing. The present invention meets this need.